Pulling or hauling vehicles have been used for decades, particularly in the form of tractors for agricultural or forestry purposes. Although the requirements made on such vehicles and the uses thereof have undergone considerable changes, the basic construction thereof has essentially remained unchanged.
Although originally a relatively high tractor weight was desired, because they were used purely as pulling vehicles and consequently the rear axle had to be adequately loaded, of late and in particular following the development of tools or implements to be directly suspended on the tractor, the weight of the tractor and the weight distribution have proved disadvantageous. By means of three-point suspension or hydraulic lifting devices, numerous means are now coupled to the rear of the tractor and during operation can be lowered onto the ground or raised when moving. These implements or tools in part have considerable weight and therefore lead to additional loading of the rear tractor axle.
If very heavy tools are hung on the rear of the tractor, there is a risk that this will cause leverage and consequently an unfavorable weight distribution which can bring about lifting of the front axle. The presently conventional countermeasure comprises fitting additional weights in the vicinity of the tractor front axle, so that the front axle load is raised. Although this is able to stabilize the tractor and prevent lifting of the front axle, it simultaneously considerably increases the total tractor weight and consequently causes very considerable ground or soil pressure. Due to the great overall weight, it is frequently necessary to have a four or all-wheel drive in order to increase the tractive power, but this only insignificantly improves the pulling capacity, because in accordance with the short construction of such tractors the vehicle weight is displaced to the rear axle due to the pulling moment and the weight distribution in operation.
As a result of the weight of the tractor and tools and the consequent considerable loading in particular of the rear axle, the soil is greatly compressed and damaged along the wheel track. This is prejudicial to the activity of soil organisms and bacteria and the field is compressed so that there is an inadequate oxygen supply and disturbed water conservation of the soil. Due to the destroyed soil capillarity, the water drainage under rainy conditions and the rising of the water during good weather are impaired. This excessive soil loading also leads to the destruction of plant growth, the obtaining of a lower yield and necessitates increased fertilizer and pesticide application. This leads to additional harming of the environment, all of which could be avoided by the use of suitable tractors and tools. Moreover, the travelling characteristics of vehicles designed in this way are very unfavorable and dangerous. This more particularly applies as a result of inadequate loading of the front axle and consequently to difficult controllability of the vehicle, particularly when travelling rapidly on roads.